Unit 3

advertisement
3.(a) Periodic Table, Isotope
abundance
chapter 3
(b) Origin of Food
A group of elements consists of all the elements in
any vertical column of periodic table.
The elements in each horizontal row of the periodic
table represent a period.
The Periodic Table(see www.webelements.com)
Isolation of Elements
• He from natural gas-looming shortage
(escapes from the atmosphere)
• Ne, Ar, Kr, Xe come from fractional
distillation of liquid air
• Radon (Ra) comes from radioactive decay
of radium
• Halogens found as ions in sea salt, ie
NaCl, KI etc.
Evaporation of Sea water
• New Zealand Salt beds, sources of Cl, Br ,
I in salts
The atomic weight of an element is the
average of the mass of all of its isotopes,
weighted for the abundance of each.
If the atomic weight of Cl = 35.5
and Cl has two isotopes :
35 Cl
17
37 Cl
17
Approximately how much of each isotope
occurs in natural abundance?
Tough Question!
•
•
•
•
Where to start?
Any suggestions?
If 50% of each isotope,
atomic weight would be?
Isotopes of Chlorine
• Let fraction of 35Cl=x, thus fraction of
37Cl=1-x
• So x(35) + (1-x)37= 35.5
• 35x +37 -37x = 35.5
• -2x= -1.5
• x=.75
Thus about 75 % 35Cl and 25 % 37Cl.
Life’s Good things Come from Chemistry!
C H O Co La Te
Food: The Macronutrients
•
•
•
•
•
•
Carbohydrates (4 calories/gram)
Protein (4 calories /gram)
Fats (9 calories/ gram)
>99% of calories come from these
------------------------------------------------Micronutrients; Essential, but in much
smaller amounts: Vitamins, Minerals
Where does our food come from?
..
. .
..
-
+
.
Origin of Carbohydrates: Photosynthesis
• 6CO2 + 6H2O  C6H12O6 +6 O2
• Glucose (a sugar) is formed
• Reaction catalyzed by chlorophyll and requires sunlight
• Balanced Equation: equal # of C, H, O on LHS and RHS
Biosynthesis of Carbohydrates
• Plants convert glucose to more complex sugars ie.
cellulose, starch
• Plants “fix” nitrogen from soil and air (78% N2, 20% O2,
all others 2%)
• Animals convert plants to protein and fats
Biosynthesis of Fatty Acids
• Complex: involve enzymes (catalysts) , ie
Acetyl Coenzyme A.
• Fats are biosynthesized by sequential
addition of 2C units.
• Palmitic acid –a C16 saturated fatty acid
requires 8 Acetyl Co A units
• Plants make these in their seed
Biosynthesis of Fats in Plants
Rapeseed (Canola) : source of a “healthy
mixture of unsaturated fatty acids
Biosynthesis of Protein
• From amino acids
• Human body can biosynthesize some
proteins (for muscle, hair, hormones)
Download